Other companies like Flash-2-Pass offer a kit similar to the Harley unit, but my personal favorite method involves a simple modification to a standard remote for your GDO. Open up the remote to access the printed circuit board, solder two wires to the pins for the activation switch, close up the remote and install it inside the fairing just like the transmitter Harley supplies in their kit. Then run the wire to a simple momentary SPST switch you can mount wherever you like. I mounted mine next to the Harley switch for the Aux (passing) lamps, you could choose a less obvious place if you like. It works directly with the garage door opener and doesn't require a special receiver like the Harley setup, and the performance is vastly superior in terms of range. My method just uses the internal battery to power the remote, but if someone wanted to get fancy they could also power the remote from the bike. Considering how long a good lithium battery lasts in a remote, I just stuck with the simple method.
One issue that needs to be addressed is that the Harley kit is old tech and isn't set up to work with the latest openers that have multifunction wall controls. It can be modified to work or you can buy an add-on product to make it work, but you can't just run the two wires from the Harley receiver directly to the opener like you could for the older openers. There are several other threads around here detailing the issue with trying to use the Harley system with openers made by Chamberlain (they make them under their own name plus others like Liftmaster, Craftsman, etc.). While it can be made to work, it doesn't work right out of the box and Harley needs to come out of the dark ages and have the system redesigned to work wirelessly with modern openers. Kind of like Homelink in automobiles.
Jerry